1)Do I need to let the car idle before swtiching it of after hard driving( fast accelleration and highish speeds), somewhere along the line I picked up the info that after heavy driving on a turbo charge motor you need to let it idle for a while to let the turbo cool down before turning it off?

2)if it is recommended that the vehicle is idled before turned off, will the ASS system not be a problem. for example lets say I accellerate hard between a few traffic lights before I stop at one, then the ASS system would create a problem by not letting the motor idle.

1)Do I need to let the car idle before swtiching it of after hard driving( fast accelleration and highish speeds), somewhere along the line I picked up the info that after heavy driving on a turbo charge motor you need to let it idle for a while to let the turbo cool down before turning it off?

2)if it is recommended that the vehicle is idled before turned off, will the ASS system not be a problem. for example lets say I accellerate hard between a few traffic lights before I stop at one, then the ASS system would create a problem by not letting the motor idle.

The following is quoted from Mark Miller's Lifetime Maintenance Schedule for BMW owners concerning the care of turbochargers.

"Lifetime turbocharger warm-up and cool-down procedures

Many of my readers who own BMWs powered by turbocharged engines ask how they can help the turbochargers last longer. They are concerned, and rightly so, with the cost of post-warranty ownership of the modern BMW and want to know how to approach it. If you want to keep the car past the warranty the best way to prolong turbocharger bearing life is to do two things:

First, use very high quality full synthetic oil in a viscosity that can withstand tremendous heat, and change it at an interval appropriate to the product, verified by oil analysis. Second, practice traditional turbocharger warm up and cool down procedures. This means allowing the engine oil to reach operating temperature before spooling up the turbos (keep the rpms low), and allowing the turbos to cool down before shutting off the engine by driving gently at low rpm for several miles before reaching the destination.

Back in the olden days, every car manufacturer with a turbocharged engine (BMW, Ford, GM, Mercedes Benz, Porsche, SAAB, Renault, etc.) detailed this warm up and cool down procedure. But those cars were bought and driven exclusively by driving enthusiasts who knew their way around cars. Car buyers have changed and today’s oil is better, but engine oil lubricated turbocharger bearings have not changed. The nature of turbocharged cars has changed as well. Back then, only sports cars, executive limousines like BMW’s E23 745i, and diesel-powered sedans had turbochargers. People who owned those cars could be counted upon to have a certain degree of automotive knowledge. Nowadays, the family sedan has two turbos to go along with the automatic transmission and the baby seat. If BMW told today’s turbo car buyers they had to follow warm up and cool down procedures first off few would understand it, secondly few would do it, and third-wise a lot of them just wouldn't buy the car.

All that being said, every turbocharged engine shares one thing in common, which is that if it is in service long enough it will eventually need a new turbocharger -- two in the case of some BMW engines." Mark Miller

In simple terms, I take this to mean don't run the car hard right after you leave the garage and don't run it hard on the way back into the garage.

This means allowing the engine oil to reach operating temperature before spooling up the turbos (keep the rpms low), and allowing the turbos to cool down before shutting off the engine by driving gently at low rpm for several miles before reaching the destination.

All that being said, every turbocharged engine shares one thing in common, which is that if it is in service long enough it will eventually need a new turbocharger -- two in the case of some BMW engines." Mark Miller

In simple terms, I take this to mean don't run the car hard right after you leave the garage and don't run it hard on the way back into the garage.

How would one perform those procedures in an urban environment where some of us are only minutes from highways where there is no sufficient time to warm up and cool down. Seems like a waste of gas and defeats the purpose of higher fuel efficiency if you have to ride around the block a few times to cool off the turbos.

How would one perform those procedures in an urban environment where some of us are only minutes from highways where there is no sufficient time to warm up and cool down. Seems like a waste of gas and defeats the purpose of higher fuel efficiency if you have to ride around the block a few times to cool off the turbos.

I suspect it's only a real issue if you've been driving the car hard. In "normal" use where you aren't revving the nuts off it, the turbos aren't working that hard anyway.

Bottom line is that the hot oil, when left to sit on the turbo bearings, will cook and pit them over time. On my old 3000GT VR-4 I installed a "turbo timer" that allowed the engine to run for a preset time after I left and locked the car. This allowed the oil to cool down before shutting off, therefore leaving the bearings in a cooler bath of oil.

My philosophy is that it really is not that big of a deal to let the car idle for a minute before turning it off. Whether it is required or not, I still do it. On a risk/reward balancing test, the risk is almost nil while the possible reward is high.

My philosophy is that it really is not that big of a deal to let the car idle for a minute before turning it off. Whether it is required or not, I still do it. On a risk/reward balancing test, the risk is almost nil while the possible reward is high.

It may not be risky to run the car for an additional minute (or at least 30 seconds for moderately driven car), but you have to spend that additional minute in the car, plus you spend some gas for that, which cancels out the saving effect of ASS.

Do we know for a fact that the water pump continues circulating water after the car is shut down, and do we know for a fact that the turbo is water-cooled?

While Mike Miller's article contains a good deal of common sense, and it jives with my intuition on the matter, it doesn't mean either of us is right. Quite frankly, I never had any respect for the man, because I started reading his articles in the late 90s when I had an E36, and he essentially insists that every BMW made since the E30 is an utter pile of crap. He spread nonstop FUD about the E36, which, from damn near a decade on the E36 M3 list, I knew was all wrong.

turbo timers and long cooling down periods are generally not required on modern turbos. I try not to put it (it being a car the runs more boost than the f30) away smoking hot and would generally let a car cool down for a couple minutes after hard running, but in normal driving I pretty much just turn my turbocharged car off. Also, I think they are more durable in general and it's quite possible for the turbo to last the entire life. The quality oil point that some have made is probably good though.